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238

TEETH OF HORSE

the premolars, with the exception of the first, resemble the molars
in their pattern. The orbit is completely surrounded by bone.
The incisors are chisel-shaped, with a pit on the free surface.
The canines are rudimentary if present. The radius and ulna
are fused, as are the tibia and fibula. Although for the sake of
uniformity a family, Equidae, is here separated from its allies, it
is quite impossible owing to the full state of our knowledge of
this group to draw a really hard-and-fast line between this family

FJCL 124. Sid view of skull of Horse with the bone removed so as to expose tlie whole
of tlie teeth, <e, Canine ; JPr, frontal; **, &, ^3t incisors ; Z, lachrymal ; m\ m2, m?t
molars ; Ma, malar or jugal; Mt&, maxilla ; Nat nasal ; oc, occipital condyle ; Pa,
parietal ; pm\ situation of the vestigial first premolar, which has been lost in the
lower, bat is present in the upper jaw ; j?m.2, j?i3, pm,*, remaining premolars ; JPMx,
premaxaia; pp> paroccipital process ; S$, squamosaL (After Flower and Lydekker.)
and tlie Palaeotheriidae. We shall deal presently with the con-
jeetmed pedigree of the Horse, which naturally involves that
family, and which presents an unbroken series from four-toed
Perissodactyles to the present one-toed Horse, the various bones
Mid teeth becoming modified in the course of the descent " with
the regularity of clockwork/* We are compelled to draw the
line n* functional second and third toes; directly these are no
need tlie animal is a Horse in the strict sense I This is
'.ami loog^ettabl^ bat necessary for practical purposes, if